This article presents a study of fatigue-crack propagation behavior in Nitinol, a 50Ni-50Ti (at. pct) superelastic/shape-memory alloy, with particular emphasis on the effect of the stress-induced martensitic transformation on crack-growth resistance. Specifically, fatigue-crack growth was characterized in stable austenite (at 120 8C), superelastic austenite (at 37 8C), and martensite (at 265 8C...

An in-vitro experiment was designed to investigate the mode of failure following shear fatigue loading of lumbar motion-segments. Human male lumbar motion-segments (age 32-42 years, n=6) were immersed in Ringer solution at 37°C and repeatedly loaded, using a modified materials testing machine. Fatigue loading consisted of a sinusoidal shear load from 0 N to 1,500 N (750 N±750 N) applied to the ...

Fatigue failures caused by cyclic stresses are commonly modeled by Birnbaum-Saunders (B-S) and Weibull distributions. Sometimes, materials with high cycle fatigue exhibit bimodal failure rates which are difficult to model with Weibull distribution. The objective of this paper is to investigate a general Birnbaum-Saunders (GB-S) distribution which covers diverse hazard rates such as increasing, ...

OBJECTIVE To test whether serum levels of selected cytokines relate to different dimensions of fatigue in patients with primary Sjögren's syndrome (pSS). METHODS Sixty female patients with pSS filled out a questionnaire to assess multiple dimensions of fatigue. Scores were compared with values in a population based control group (n = 139). Levels of interleukin (IL)1beta, IL2, IL6, IL10, and ...

Lower extremity neuromuscular fatigue purportedly increases anterior cruciate ligament (ACL) injury risk through promotion of extreme landing mechanics. However, the impact of fatigue on muscle groups critical to the landing strategy remains unclear. This study examined the effects of isolated hip rotator and triceps surae fatigue on lower extremity landing biomechanics. Sixteen healthy females...

In this paper, a type of response spectra in which fatigue damage is the ordinate is reviewed. Computation of this Fatigue Damage Spectrum (FDS) in both the time and frequency domains is discussed. The method of Fatigue Damage Equivalent vibration Testing (FDET) is discussed using the FDS as the measure of environment severity. Improvements in each technique over previous work are introduced an...

In the paper, genetic algorithm is introduced in the study of network authority values of BP neural network, and a GA-NN algorithm is established. Based on this genetic algorithm-neural network method, a predictive model for fatigue performances of the pre-corroded aluminum alloys under a varied corrosion environmental spectrum was developed by means of training from the testing dada, and the f...

The possible role of enteroviral persistence in the etiology of the chronic fatigue syndrome (CFS) was investigated by serological testing, VP-1 antigen testing, and polymerase chain reaction (PCR) analysis of stool specimens as well as by viral cultures of stool--both direct and after acid treatment. No differences between 76 patients with disabling unexplained fatigue and 76 matched controls ...

In probabilistic design of materials for fracture-critical components in modern military turbine engines, a typical maximum design target risk (DTR) is 5 10 8 component failures/engine flight hour. This metric underscores the essential role of safety in a design process that simultaneously strives to achieve performance, efficiency, reliability, and affordability throughout the life cycle of th...

Surface electromyographic (sEMG) activity of the biceps muscle was recorded from 13 subjects. Data was recorded while subjects performed dynamic contraction until fatigue and the signals were segmented into two parts (Non-Fatigue and Fatigue). An evolutionary algorithm was used to determine the elbow angles that best separate (using Davies-Bouldin Index, DBI) both Non-Fatigue and Fatigue segmen...